81913393 has 2 divisors, whose sum is σ = 81913394. Its totient is φ = 81913392.

The previous prime is 81913379. The next prime is 81913397. The reversal of 81913393 is 39331918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81866304 + 47089 = 9048^2 + 217^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81913393 is a prime.

It is not a weakly prime, because it can be changed into another prime (81913397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40956696 + 40956697.

It is an arithmetic number, because the mean of its divisors is an integer number (40956697).

Almost surely, 2^81913393 is an apocalyptic number.

It is an amenable number.

81913393 is a deficient number, since it is larger than the sum of its proper divisors (1).

81913393 is an equidigital number, since it uses as much as digits as its factorization.

81913393 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 37.

The square root of 81913393 is about 9050.6018031952. The cubic root of 81913393 is about 434.2951424577.

The spelling of 81913393 in words is "eighty-one million, nine hundred thirteen thousand, three hundred ninety-three".